Recent findings from this laboratory suggest that infant rat pups' ultrasonic vocalization, oxygen utilization, respiration and non-shivering thermogenesis are functionally interrelated. We hypothesize that the pups' vocalizations are primarily the result of an adaptive, laryngeal/respiratory maneuver associated with phases of increased metabolic heat production and low oxygenation. To better understand the temporal and causal relationships among these correlated variables, we shall combine modern thermal imaging methods with other non-invasive techniques for measuring oxygen consumption, respiration and vocalization. Thermal imaging promises to provide real-time, highly accurate data on thermogenesis and patterns of body-warming and cooling that may explain changes in infant respiration and vocalization. A series of developmental and mechanistic analyses address the special problems, associated with the transition from fetal adaptations to infant adaptations. Thermal imaging will also be applied to postnatal behavior of infants during learning and in social settings, where traditional measurement techniques cannot be used due to mechanical interference. Together, these studies should provide new perspectives on perinatal behavior and physiology, particularly in relation to issues of respiration, thermal balance and communicatory signals.